Production of aromatics from paraffin hydrocarbons



OIL

ABSORBER ZONE 42 P. s. VILES Filed Sept. 28, 1956 AIR REACTION V I vZONES STEAM PRODUCTION OF AROMATICS FROM PARAFFIN HYDROCARBONS FURNACEI5 3 BURNERS I7 Aug. 18, 1959 HYDROCARBON FEED ZONE

INVENTOR.

PR ENTISS S- VILES,

AND RECOVERY ZONE SEPARATION ZONE 34 FLUE GAS SEPARATION COOLER REACTORCYCLONE SEPARATOR HEAT EXCHANGER COOLER FIG. I.

FIG. 2.

HYDROCARBON FEED Unite States Patent PRODUCTION OF AROMATICS FROMPARAFFIN HYDROCARBONS Application September 28, 1956, Serial No. 612,607

12 Claims. (Cl. 260673) The present invention is concerned with theproduction of unsaturated hydrocarbons. More particularly, the inventionrelates to the conversion of hydrocarbons in the presence of sulfurdioxide. In its more specific aspects, the invention is concerned withthe production of unsaturated hydrocarbons from saturated hydrocarbonsin admixture with sulfur dioxide.

The present invention may be briefly described as a method for formingunsaturated hydrocarbons, such as olefins and aromatics, by forming amixture of a saturated hydrocarbon, such as a paraflin, having amolecular weight of at least 30 with sulfur dioxide and then contactingthe mixture with a cobalt molybdate catalyst at a temperature in excessof about 800 F. to form a prodnot containing unsaturated hydrocarbonsand recovering the product.

The feed hydrocarbon employed in the present invention may suitablyrange from about the boiling point of ethane up to about 750 F. The feedhydrocarbon may be a normally gaseous hydrocarbon, such as one having amolecular weight of no less than about 30, and homologues thereof andmay comprise a normally liquid hydrocarbon. A preferred feed stock willinclude ethane and higher boiling materials, natural gas components,normally liquid hydrocarbons, such as those boiling in the kerosene andgasoline boiling range as well as gas oil hydrocarbons. It will bedesirable and possible to form olefins from the paraffinic hydrocarbonsincluding ethane, propane, butane, pentane, and the like while thehigher boiling members, such as heptanes, hexanes, octanes, and thehigher members of the homologous series will tend to form unsaturatedring compounds, such as aromatics.

The catalyst employed in the present invention is cobalt molybdatepreferably on a support. By cobalt molybdate it is to be understoodthat, within the purview of the present invention, cobalt molybdate is amixture of cobaltous oxide (000) and molybdic trioxide (M00 Thecobaltous oxide and molybdic trioxide may be employed in a preferredratio of mol per mol as the catalyst but the ratio of cobaltous oxide tomolybdic trioxide may range from 0.1:1 to 120.1 mol of cobaltous oxideper mol of molybdic trioxide.

The amount of cobalt molybdate on the support may range from about 1.0to 25.0 weight percent with a preferred amount of approximately 15.0% byweight of the total catalyst.

The supports for the cobalt molybdate may suitably be alumina, zirconia,magnesia, silica, silica-alumina, Filtrol, kieselguhr, Floridan, and thelike. Preferred supports are pure alpha and gamma alumina.

The temperatures employed in the practice of the present invention maysuitably fall within the range of about 800 to about 1600 F. with apreferred temperature range of 1100" to about 1400 F. Quite satisfactoryrer 2,900,427 Patented Aug. 18, 1959 sults have been obtained at about1300 F. The pressures may range from about 0 pounds absolute to about1000 pounds per square inch gauge.

The feed stock may be contacted with the catalyst at a suitable feedrate which may be in the range from about 1 to about 500 volumes of feedper volume of catalyst per hour with a preferred v./v./hour from about50 to about 100. The reaction may be conducted in either the vapor orliquid phase but vapor phase is to be preferred for the low boilinghydrocarbons.

The invention may be practiced in various types of equipment. Forexample, the reaction zone may have a catalyst bed arranged therein as afixed bed or the reaction may be conducted in the so-called fluidizedpowder technique wherein the cobalt molybdate is suspended in vaporizedhydrocarbons. Furthermore, the reaction may be conducted in a suspensionor in a slurry.

The reaction zone employed in the present invention may be constructedof material which provides a nonreactive surface with the product orwhich forms'with the product a surface which does not react further withthe product. Thus, with steel or ferrous metal reaction walls andconduits of such nature, the product may react therewith initially toform a non-reactive coating thereon. Preferably, the reaction zone wallsand the interior of conduits employed for transporting the product aresuitably constructed of non-reactive material such as glass, ceramicware, and the like or ferrous metal equipment may be lined with suchnon-reactive material.

The amount of sulfur dioxide employed in the practice of the presentinvention may suitably range from about 0.5% to about 50% by weight ofthe mixture with the hydrocarbon. When employing vapor phase operations,the amount of sulfur dioxide may suitably range from about 10% to about50% by weight of the mixture with a preferred range from about 15% toabout 45% by weight of the mixture, whereas with liquid phase reactionconditions, the amount of sulfur dioxide in the mixture may range fromabout 0.5 to about 10% by weight of the mixture with a preferred rangefrom about 2.5% to about 7.5% by weight of the mixture.

The present invention will be further described by reference to thedrawing in which:

Fig. 1 is in the form of a flow diagram illustrating one mode of theinvention; and

Fig. 2 is in the form of a flow diagram illustrating a preferred mode.

Referring now to the drawing and first to Fig. 1, numeral 11 designatesa charge line by way of which a feed hydrocarbon is introduced into thesystem. Line 11 is controlled by a valve, such as 12. Leading into line11 is line 13 controlled by valve 14 by way of which a suitable amountof sulfur dioxide is admixed with the hydrocarbon in line 11. Themixture of hydrocarbon and sulfur dioxide is discharged into a furnace15 'PIO'. vided with a coil 16 and with gas burners 17 by Way of whichthe temperature is raised to a temperature in the range given supra. Theheated gaseous or vaporous mixture discharges from furnace 15 by way ofline 18 and may be routed into reaction zones 19 and 20 by way of lines21 and 22 controlled, respectively, by valves 23 and 24. Beds 25 and 26comprising a supported cobalt molybdate catalyst are arranged inreaction zones 19 and 20. The gaseous reactant mixture contacts the beds25 and 26 under the conditions stated hereinbefore to produce a productcontaining a substantial amount-0f unsaturated materials. Theunsaturated product discharges from zones 19 and 20 by way of lines 27and.

28 controlled, respectively, by valves 29 and 30 into line 31 and by wayof branch line 32 containing a valve 33 into a separation zone 34. Line32 suitably contains a temperature quenching means, such as cooler 35,by way of which the temperature of the product is reduced rapidly from atemperature within the range of 800 to 1600 F. to about 150 F. Within atime no greater than about l second to stop the reaction. Instead ofemploying, a cooler as a quench zone, a suitable quench liquid 'may beemployed. Suitable quench liquids may include .steam and non-reactivehydrocarbons, such as gas oil and the like.

The quenched and cooled product in separation zone 34 is separated intoa gas phase and a liquid phase. The gas phase is withdrawn by way. ofline 36 and discharged into an absorption zone, such as 37, where thegaseous product is contacted with a suitable absorption medium, such asa hydrocarbon introduced by line 38 controlled by valve ,39. Fixed gasesare removed from absorption zone 37 by way of line 40, whereas theenriched absorption oil is discharged by way of line .41 into astripping zone 42 which is provided with a suitable temperatureadjusting means, such as a heating coil 43. The absorbed hydrocarbonsare removed from the absorption medium in Zone 42 and aredischarged fromzone 42 by Way of lines 44, 45 and 46 as may be desired. The strippedabsorption medium is then recycled by way of line 47 and by way of line38 for reuse in the process.

/ The liquid phase in zone 34 is discharged therefrom by way of line 48into a distillation zone such as 49. Distillation zone 49 is shown as asingle fractional distillation tower but it is understood to include, ifdesired, a plurality of fractional distillation towers, each providedwith all auxiliary equipment usually found associated with the moderndistillation tower. Such equipment will include means for inducingreflux, condensing and cooling means and suitable internal vapor-liquidcontacting means, such as bell cap trays, plates, and the like.Distillation zone 49 is shown as being provided with a temperatureadjusting means as illustrated by heating coil 50 and is provided withlines 51, 52 and 53 as well as a draw-01f line 54 for separation andwithdrawal of products.

From time to time the beds 25 and 26 may become fouled with carbonaceousdeposits resulting from the reaction. When that occurs, the valves 12and 14 will be closed and valves 55 and 56 in manifold 57 will be openedallowing a mixture of steam and air to be discharged by way of line 58into-line 18 and thenceinto lines 21 and 22 to cause and support acombustion operation in the beds 25 and 26 to burn off the carbonaceousdeposits from the catalyst. Since the valve 33 would be closed, valve 59in line 31 would be open allowing discharge of the flue gas.

Referring now to Fig. 2, numeral 60 designates a charge line controlledby valve 61 by way of which a hydrocarbon of the type illustrated isintroduced into the system and is admixed with sulfur dioxide introducedby way of line 7 62, controlled by valve 63, the mixture passing throughline 64 into a heating means or heat exchanger 65. The heated gaseousmixture discharges by way of line 66 into a reaction zone 67 of thefluidized type in admixture with finely divided or powdered cobaltmolybdate catalyst introduced by line 68, controlled by valve 69.

The cobalt molybdate catalyst, when a fluidized system is used, may haveparticle diameters suitable for fluidization, for example, particlediameters in the range from about 1 to about 120 microns with asubstantial or major amount of the catalyst particles being in the rangeof about 20 to about 120 microns to insure proper fluidization.

The mixture of S hydrocarbon, and catalyst in the V 4 converted insubstantial amounts to unsaturated material. The reacted mixture passesinto a separation zone such as a cyclone 71 provided with a dip leg 72in the upper part of zone 70 which efiects a separation between theproduct and the catalyst, the product being discharged from zone 67 byway of line 73 in heat exchange with the feed in heat exchanger 65, thefeed being introduced by line 64. The partially cooled product thendischarges by line 74 into a cooler 75 and is then introduced by line 74into a separation and'recovery zone 76. Separation and recovery zone 76may include absorption and distillation zones and/or solvent extractionzones and the like by way of which recovery and separation and/orpurification is made among the several hydrocarbons which will be foundin the product.

The several products may be separated as desired and Withdrawn by way oflines 77, 78, 79 and 80 for further use and/ or purification.

The catalyst is withdrawn from reaction zone 67 by way of line 81 andmay be admixed with a fluidizing gas, such as steam, introduced by line82, controlled by valve 83 and the mixture of steam and catalyst isdischarged into a regenerator 84 wherein a combustion operation ismaintained by air introduced by line 85 containing a blower 86. Thecombustion operation in regenerator zone or vessel 84' efiectivelyremoves the carbonaceous deposits from the catalyst, the regeneratedcatalyst being withdrawn from zone 84 by way of funnel member 87 andconduit 88 which connects to line 68.

Products of combustion are withdrawn and discharged from regenerator 84by way of line 89.

It is preferred to employ the fluidized operation although both modesare suitable.

It is understood that any one of the several separated fractions may befurther treated such as with a selective solvent for olefins or with aselective solvent for aromatics to purify and concentrate suchcompounds. For example, where a product, such as a C fraction includingolefins, is withdrawn, such fraction may suitably be treated withsulfuric acid of a suflicient strength to absorb the olefins and toallow the concentration and recovery thereof. Where the selectedfraction includes aromatics, it may suitably be treated with a solventwhich is selective for concentration of aromatics, .such as sulfurdioxide, phenol, and the like.

The present invention will be further illustrated by runs in whichethane was contacted with an alumina supported cobalt molybdate catalystarranged as a bed in a reaction zone. In one run, the ethane was chargedas is and in another run the ethane was admixed'with sulfur dioxide.

Reaction conditions and analysis of the product recovered from thereaction under the conditions given are shown in Table I:

Table I Charge Product Charge Product Temp. F. 1, 300 1. 300 PressureAngus; Atriioser 0 erlo Charge Rate, v./v./Hr p p 195 Mol. percent:

Sulfur Dioxide 41.5 Carbon Dioxide 0.03 0. 1 0. 55 Hydrogen Sulfide 0.04 0. 2 0.02 Carbon Monoxide 0. 75 0. 24 1.6 46.62

0.30 97. 91 0. 6 10.90 0.30 9.86 0. 05 1.8 3.28 0. 65 53.9 6. 14 0. 29.04 0. 15 0. 1 4. 24 3.23 0.07 1.16 Butylenes 0. 01 7. 04 Iso-pentan 0.04 0. 44 n-pentane 0. 03 0. 03 0. 18 Pentylenes 0. 02 0. 01 0. 79Cyclopentane and Heavier. 0. 06 0. 47

Comparing the first two columns of data, it will be seen that, wheresulfur dioxide was absent from the ethane, the ethane was substantiallycompletely converted to hydrogen with the formation of minor amounts ofother hydrocarbons. However, comparing the data in columns 3 and 4,where a substantial amount of sulfur dioxide was present, it will beseen that the ethane was largely converted to hydrocarbons of a highermolecular Weight and in an unsaturated condition. It is to. be notedthat substantial quantities of carbon monoxide were formed. The hydrogensulfide formed during the reaction reacted with the steel walls of theconduits used to. transport the reaction product from the reactionvessel.

Runs were then made employing propane as the feed. In one run thepropane was charged to a bed of alumina supported cobalt molybdate in areaction vessel in the absence of sulfur dioxide. In another operation,sulfur dioxide was admixed with the propane. and charged to the reactionvessel in contact with the bed of cobalt molybdate. Operations withadmixtures of sulfur dioxide were conducted under various charge ratesas set out in the following table:

Table III Charge Stoek Xylene Xylene Xylene Rafiinate RalfinateRafiinate Charge Rate, ce./Hr. 400 400 Temperature, F-.. 1000 1000Pressure, p.s.i.g '200 200 Liquid Product: Yield, cc., Hr 265, 260 GasYields, Cu. Ft./Hr 4. 6 4.4

Xylene Liquid Liquid Ralfinate Product Product Liquid Sample Analysis,Mol

Percent:

Benzene.- .V 2.15; 13.14 Toluene. 8 10 10. 91 Xylenes 17-; 65 23. 93Total C9 Aromatics 7. 88 Tot. 1 Aromatic 0. 41 0. 63 Total Aromatics....4 36. 19 47.- 80 Total N aph thenes plus Olefins 28. 1 16. 45, 16, 02Total Paratiius 69. 5 47. 36 36 17 in the data, in the second columnshown in Table III the raflinate had been washed with caustic to removeall sulfur dioxide Whereas in the third column of data the Table [1Charge Product Charge Product Charge Product Temp., F 1300 1300 PressureAtmos- Atmospheric pherlc Charge rate, v./v./hr 10 M01. percent:

ultur dioxide Carbon dioxide 4. 77 Hydrogen sulfide- 0. 4 0.03 arbonmonoxide. 16.13 27. 64 itrogen 0. 70 0. 71 37. 75 30. 32. 83 21. 92 4.71 6. 26 0. 59 2, 51 3. 57 4. 43 2. 83 0. 34

From the data in Table II, it will be clear that where sulfur dioxidewas not present in the propane, the propane was substantially completelyconverted to hydrogen and methane with small amounts of otherhydrocarbons and carbon monoxide being formed. However, observing column4 where the feed stock set out in column 3 was employed which contain14.8 mol percent of sulfur dioxide, substantial amounts of heavierhydrocarbons and olefins were produced. Again comparing the fifth columnwhere a 43.1 mol percent of sulfur dioxide was present with the sixthand seventh columns, again it will be seen that substantial quantitiesof heavier hydrocarbons and olefins were formed.

It will be noted that in the several runs the charge rate in v./v./hourwas increased from 100 to 300 v./v./hour with most desirable resultsbeing obtained at the short contact times which favor the production ofheavier hydrocarbons and olefins as shown by the data.

Other operations were conducted with a raflinate obtained by solventextraction with sulfur dioxide of a xylenes fraction. This railinate wassubstantially completely octane and boiled in the range from about 250to about 320 F. The raffinate fraction was then contacted with a bed ofalumina supported cobalt molybdate and a product obtained which was thenanalyzed. The results from these runs are shown in Table III:

by weight dioxide was present, substantially increased yields ofaromatics were obtained as compared to the run where the sulfur dioxidewas absent. It is to be noted that the naphthenes and olefins content ofthe product from the two runs were substantially unchanged indicatingthat the sulfur dioxide acts to convert paraflins to unsaturatedcompounds such as aromatics where the chain length is suflicient to formthe ring compound.

The present invention is of considerable importance and utility in thatparaffinic hydrocarbons and particularly straight chain paraffinichydrocarbons which are less valuable than olefinic and aromatichydrocarbons may be converted in substantial yields to the more valuablecompounds. The olefins and aromatics are more valuable than theparaffins because the olefins and aromatics have higher octane numbersthan the straight chain parafiins and may suitably be used as blendingagents in motor and aviation fuels and, furthermore, the olefins and thearomatics are more reactive than the paraflins and may be used inalkylation and other conversion operations.

The nature and objects of the present invention having been completelydescribed and illustrated, what I wish to claim as new and useful and tosecure by Letters Batentisa .7 o

1. A method for forming aromatic hydrocarbons from paraflinichydrocarbons of lower molecular weight which comprises forming a mixtureconsisting essentially of a normally liquid paraflinic hydrocarbonhaving a chain length sufficient to form an aromatic ring and having aboiling range up to 750 F. and sulfur dioxide in an amount within therange from about 0.5% to about 50% by weight of the mixture, contactingsaid mixture with a catalyst consisting of aluminasupported cobaltmolybdate at a pressure from about pounds absolute to about 1000 poundsper square inch gauge, at a rate from about '1 to about 500 volumes ofmixture per volume of catalyst per hour and at a temperature within therange from about 800 F. to about 1600 F. to form a product containingaromatics and heavier hydrocarbons, and recovering said product.

'2. A method in acco dance with claim 1 in which the Hydrocarbon mixtureis contacted in the liquid phase.

3. A method'in accordance with claim 1 in which the hydrocarbon mixtureis contacted in the vapor phase. 4. A method in accordance with claim 1in which the mixture is contacted with the catalyst in a fixed bed.

5. A method in accordance with claim 1 in which the mixture is contactedwith the catalyst in a fluidized bed.

6. A method in accordance with claim 1 in which the 7 catalyst is cobaltmolybdate on alpha alumina.

7. A method in accordance with claim 1 in which the catalyst is cobaltmolybdate on gamma alumina.

8. A method for forming aromatic hydrocarbons of higher molecular weightfrom parafiinic hydrocarbons of lower molecular weight which comprisesforming a mixture consisting essentially of a parafrinic hydrocarbonboiling within the range from about theboiling point of hexane to about750 F. and sulfur dioxide in an amount within the range from about 0.5%to about 10% by weight of the niix'ture, contacting said mixture with acatalyst. consisting. ofalumina supported cobalt molybdate at a'pressurefromabout 0. pounds absolute to about 1000 pounds per'square inch" gaugeat a-irate'from about 1 to about 500*volu'mes of mixture 'pervolume ofcatalyst perhour andat a temperature within the range from about 800".F.1o'ab0ut 1600 F. to form a product con taining i aromatic hydrocarbonsheavier than the 'paraf finicihydrccarbon and recovering said product.""9'..A methodfor forming aromatic hydrocarbons of higher molecularweight from paratfinic hydrocarbons of lower molecular weight whichcomprises forming amixture consisting essentially of a normally liquid.paraflinic hydrocarbon in the gasoline to gas oil boiling range andsulfur dioxide'in an amount within the range from about 0.5 to about 10%by weight of the mixture, contacting said mixturdwith a catalystconsisting of aluminasupported cobalt molybdate at a temperature withinthe range from about 800-F. to about 1600' F'.'to form'a productcontaining aromatic hydrocarbons heavier than the normally liquidparaflinic hydrocarbon, and recovering said product;

10. A method in accordance withclaim 1 in which the normally liquidparatfinic hydrocarbon is hexane.

11. A method in accordance with claim 1 in which the normally liquidparafiinic hydrocarbon is heptane.

12. A method in accordance with claim 1 in which the normally liquidparatfinic hydrocarbon is octane.

References Cited in the file of this patent V UNITED STATES PATENTS'2,441,297 Stirton May 11, 1948 2,604,438 -Bannerot -2.- July 22, 19522,720,550 Danforth Oct. 11, 1955 2,772,315 Hadden Nov. 27, 1956

1. A METHOD FOR FORMING AROMATIC HYDROCARBONS FROM PARAFFINICHYDROCARBONS OF LOWER MOLECULAR WEIGHT WHICH COMPRISES FORMING A MIXTURECONSISTING ESSENTIALLY OF A NORMALLY LIQUID PARAFFINIC HYDROCARBONHAVING A CHAIN LENGTH SUFFICIENT TO FORM AN AROMATIC RING AND HAVING ABOILING RANGE UP TO 750* F. AND SULFUR DIOXIDE IN AN AMOUNT WITHIN THERANGE FROM ABOUT 0.5% TO ABOUT 50% BY WEIGHT OF THE MIXTURE, CONTACTINGSAID MIXTURE WITH A CATALYST CONSISTING OF ALUMINA-SUPPORTED COBALTMOLYBDATE AT A PRESSURE FROM ABOUT 0 POUND ABSOLUTE TO ABOUT 1000 POUNDSPER SQUARE INCH GAUGE, AT A RATE FROM ABOUT 1 TO ABOUT 500 VOLUMES OFMIXTURE PER VOLUME OF CATALYST PER HOUR AND AT A TEMPERATURE WITHIN THERANGE FROM ABOUT 800* F. TO ABOUT 1600* F. TO FORM A PRODUCT CONTAININGAROMATICS AND HEAVIER HYDROCARBONS, AND RECOVERING SAID PRODUCT.